Eusocial & Colony Behavior in Ants

Biology 342 Fall 2012

Celina Ortiz & Jason Swinderman

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• Phylogeny
• Ontogeny
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Ontogeny

Ontogeny describes lifetime development of an animal as determined by the interaction between its genes and environment. From the time it's an embryo till it's dying breath, ontogeny encompasses the changes an organism experiences during it's span of life.

Ants develop into different castes (small workers, large workers, or new queens) based largely on the nutrition they receive as larvae. This process by which nutrition determines subsequent caste development is called trophogenesis. Those fed more insects than seeds are more likely to become larger individuals. For example, Queen larvae receive more food and "royal jelly", a high sugar diet with lots of pantothenic acid and biopterin, while worker ants receive less of either. This is why generally Queen ants are much larger than worker ants. However, genetic differences also contribute and bias the larva's developmental pathway. Even once a caste is determined, nutritional, social (colony size), and genetic factors contribute to how large an individual may grow.

All eusocial insects are divided into castes. Ant colonies are no different. Once an ant has developed into a caste, it cannot change caste (with the exception of Princess into Queen). Ants in different castes have individual jobs and distinct phenotypes appropriate to their status. The difference in morphology within a species is called polyphenism. In ants, these castes are Queen, Worker, Soldier, Drone and Princess.

	Queen Queen ants are the founders of all colonies, and after mating only once, they are able to produce millions of eggs for years. They can produce up to 1,000 eggs a day, and can life from 1 year to 30 years.
	Worker Worker ants are small sterile females. They perform most of the work in the colony, including taking care of the brood and foraging for food, as well as expanding the colony. Workers may be all alike (monomorphic) or of varying sizes and shapes. Though sterile, they may lay eggs which are fed to larvae or to the queen. These are called trophic eggs.
	Soldier Soldier ants are large sterile females. They characteristically have big mandibles and a bulkier body. They protect the colony from predators and clear a pathway for smaller worker ants to reach food.
	Drone Drones are the only males in a colony. They are born from un-fertilized eggs, and thus have only half the chromosomes a female ant does. Their sole purpose is to find a virgin princess and mate, whereupon they die.
	Princess Princesses are unfertilized virgin queens. Upon mating, she will crawl on the ground to find a place to lay her eggs and form her own colony. Her wings fall off and serve as food for her new brood.

Social Learning and Hunting Behavior in Ants

The ant species Myrmica rubra learns what is prey and what isn't from more experienced adults in the colony. Without this learning, only 5% (7 out of 123) of naive ants caught and killed jumping springtails over the course of a day in a close container. Otherwise, they "responded to springtails as conspecific animals rather than potential prey". This experiment demonstrates that hunting behavior must be taught to M. rubra, and thus is an ontogenic development.